Setback switch



29, R. G. FERRIS SET-BACK SWITCH Filed March 17, 1943 lll,

INVENTOR ROBERT G. F ERRIS Patente-cl Apr. 29, 1947 UNITED STATE-s PTENT ermee Robert Gi F'iis; Harvard; 111g; assigiorwto" the United States oir'` America; a'sL represented by' the Secretary of Navy 1: j rnisirivehnoii-rc1atcd to switches roi" csc inf projectiles' and has particular reference to' a novel setback-operated switch for this use which positive' in actiona'nd is held securely Ainj its operative position after itihas" been actuated by a force of setback. Y

Qne object of the inve'ntio'n is to provide a switch'A having a stud `of electrically conducting material which1 is shifted by a force of setback to penetrate twosuperirnposed conducting pieces separated by a'cthin flat insulating piece, the stud having a periphery' of irregular conguration whereby' it makes good electrical contact with' thefflat conducting pieces and is held in contact with both pieces during" the' flight ofthe projectile.

` Switcheshave been devised heretofore inwliich a" weight is dropped down a well to'drive a circuit-closing pin through `two insulated Vcopper gauge disks for closing" a circuit and exploding a detonator inthewell, as' disclosed in Barab PatehtNoL 1,458,925. These prior switches are intended to energize the circuit and explode the detonator immediately upon closing of the switch, and, therefore, it is not necessary to provide means for holding the pin in itsv circuit-closing position. However, in a safety switch for pro; jctiles, it is necessary to maintain the switch positively inits'closed position after it has been actuated by the force of` setback incident to firing the projectile, sothat the detonating circilit4 is" armed duringilight of theprojectile. cordin'gly, the prior swtchesoflthe type described are `not suited for use as safety switches in projectiles. c l ,Y

Another object oi the invention,` therefore, resides in the provision of anovel safety switch for projectiles in which thepenetrating stud or pin is retained positively in its circuit-closing position against the forces of reverse setback, vibration, etc. encountered in projectiles duringV their night.

`it further obj ect" offthe' invention is to provide 'a novel setbackfoperated switch of `simple and inexpensive constructio'n adapted to be manufactured'in largeoluairitities` and which is positive and reliable in operation. Y

These andfurther objectsvof my invention will be better unde'istoodby' rference' to the accompanyingidrawing, in which@ ,c Fig." 1 is" a?schematicview"ofl a-projctlimbodying one form of the new switch;

Fig. 2 is a perspective, exploded View of the switch shown in Fig. 1;

Fig. 3 is a-viti-cais'cotionoi vic-'w of inc switch initsop-circuit' position, and

Figi-'41s a similar vie'w snowing inc switch' in its closed-'circuit position; c i c Rf ingttoflifig' l', the numeral IU designates tHe' asing of an" plosive projectile containing a'detnator Il operable electrically by a current s'rc, suoli" as' a' battery l2. A normally open switch i`3` in series withl the battery and the detonator is adapted to be closed by suitable means` (not shown), such as a radio apparatus responsive' to proximity of a target tothe pro-` jectile,` as4 disclosed in a copending application of MJA". Tuve" et al,SerialNO. 471,388, filed Jan. 6.,' 19213. vIt will b understood that when the sivi't'cl'i` l3'1is closed, the detonating circuit is ener'gfiz'd by the battery to re the detonator Il a'die'Xplde the charg ih thepojeotil.

fr c setback switch is of the invention, as shlo is` included in the detonating circuit in the projectile tofprv'ent premature explosion of tli detoiiator due to'accidental closing of the operating-switch i3.'` The switch E5 comprises a pair' ofc'onlducting discs land I'l separated by a ffrangibic insulating disc la; tncdiscs being sccured iitlfie' projectile Aby any' suitable means (not shown). wire IB'is connected to the conductirigjdisc le; esoy-'moans of solder 2o, andloods tthe ngative side of the battery. The other condubting disc Il is connected to a wire 2f| by a csblde'edjoiiit" 22, and the wire 2| is connected throigl'itli switch I`3fand" the detonator tothe positive side' of the battery'.

Inthe' cetra'liportions of the conductingdiscs I`6I and IT are yaligned openingsv 2li' and 25, respectively`,*separated` by the insulating disc4 I8". A'piercing' stud 26', which maybe hardened and brass plated, `isdisl'ocvs'ed in front of the disc I6 inline with the openings'rZ' and 25; the 'stud bein'gdoosely' mounted' in the projectile in anysuitab'l whereby it isl movable longitudinally under a force" o i setback. The stud 26 has a Eeral'fslraoe of virregular contour" which may takevarious forms, for a purpose" to'be de sc'ribed`pre`sri't1yl` As shown, the peripheralsurface of the stud is provided with spiral'flutes or groovesA 26 and tapers gradually to the' rear totiardL the;` discs.f At its' rear end, the stud is foiiiicci witii a reduced poriioii'or guido 21 which fits loosely in the'dis'c opening 24 to maintain the stud alig'ifimenti with tl'i openingsl The main body* ofthei'stud is' somewhat larger in diameter than the opening 24 and has a shoulder 28 which normally rests on the front disc I 6 around the opening.

The operation of the switch is as follows: Normally, the conducting discs IB and I1 are maintained in non-conducting relation by the insulating disc IB, so that the detonating circuit cannot be energized accidentally by premature closing of the operating switch I3. Also, the stud 26 is held in front of the discs by the shoulder 28. When the projectile is fired from a gun, the resulting force of setback causes the stud 26 to move rearwardly against the discs, with the result that the enlarged portion of the stud enters and enlarges the opening 24 in the front disc, penetrates the insulating disc I8, and then enters and enlarges the opening 25 in the other conducting disc, as shown in Fig. 4. The rearward movement of the piercing stud is preferably limited, as by means of a stop 3U, to prevent the stud from passing completely through the discs. When the stud has moved through the rear disc I1, it is in contact with the two conducting discs and thus forms a conducting path between them. The detonating circuit is then armed and ready to explode the detonator I I upon closing of the operating switch I3 when the projectile approaches a target.

The spiral fluting or other irregular configuration of the periphery of the stud 26 is an advantageous feature of my invention. One function of the spiral fluting is to insure a good electrical contact between the stud and the conducting discs I6 and Il. Another important function of the spiral fluting is to hold the stud positively in its closed-circuit position after it has moved through the discs under the action of a force of setback. During the flight of the projectile, the parts in it are acted upon by centrifugal force, due to rotation of the projectile, and also by reverse setback or creep, with the result that the stud 26 might be loosened and moved from its circuit-closing position unless it is held positively and securely in this position. If the stud were accidentally moved from its closed-circuit position during the ight of the projectile, it would be impossible for the fuze to explode the main charge. Such accidental movement of the piercing stud from its circuit-closing position is prevented in the new switch by providing the stud with an irregular conguration on its periphery. More particularly due to the spiral grooves in its periphery, the stud acts as a screw when forced into the discs. The discs IB and I1 may be made of a soft metal, such as copper, to cause the spiral grooves to give the stud a twist as it penetrates the discs, whereby the stud is held securely in its nal position. The taper of the stud provides a wedging action in the discs and results in a rmer electrical contact when the stud is driven through the discs.

Attention is called to the fact that the spring action of disc I5 absorbs the force produced by the stud on a drop test, due to the short time this force is exerted. However, force applied over a longer period of time, as in a projectile under acceleration from a gun, will result in the movement of the stud through the discs for puncturing the insulation and closing the circuit. The discs I6 and I1 are to be supported only at their peripheries.

I claim:

1. A setback operated switch comprising two electrically conducting discs, a frangible insulating disc between said conducting discs, and piercing means having a periphery of irregular configuration and movable by setback to pierce said discs and form an electrically conducting connection between the conducting discs.

2. A setback operated switch comprising two electrically conducting discs, a frangible insulat- 5 ing disc between said conducting discs, and piercing means having spiral grooves formed in its periphery and movable by setback to pierce said discs and form an electrically conducting connection between the conducting discs.

3. A setback operated switch comprising two electrically conducting discs, a frangible insulating disc between said conducting discs, and a tapered piercing stud having a periphery of irregular conguration, the stud being movable by setback to pierce said discs and form an electrically conducting connection between the conducting discs.

4. A setback operated switch comprising two electrically conducting discs, a frangible insulating disc between said conducting discs, a piercing stud having a periphery of irregular contour and tapered toward its penetrating end, said piercing stud being movable by setback to pierce said discs and form an electrically conducting connection between the conducting discs, and a stop for limiting movement of the stud to dene the closed circuit position of the stud.

5. A setback operated switch comprising two electrically conducting discs, a frangible insulating disc between said conducting discs, a pierce ing stud having a periphery of irregular contour and tapered toward its penetrating end, said piercing stud being movable by setback to pierce said discs and form an electrically conducting connection between the conducting discs, and means for aligning the stud relative to the discs.

6. A setback operated switch comprising a pair of electrically conducting discs having aligned openings, a frangible insulating disc between the conducting discs, and a piercing stud aligned with the openings and having a periphery of irregular contour, the stud being movable by a force of setback to enter and enlarge said openings and penetrate the insulating disc to form an electrically conducting connection between the conducting discs.

7. A switch including a pair of electrically conducting elements having axially aligned openings and an intermediate, frangible, insulating element obstructing said openings, and a piero ing stud larger in diameter than and aligned with said openings, movable under set-back to pierce the elements and electrically connect the conducting elements.

8. A switch including a pair of electrically conducting elements having axially aligned openings and an intermediate, frangible, insulating element obstructing said openings, and a piercing stud larger in diameter than and aligned with said openings, movable under set-back to pierce the elements and electrically connect said elements, and said stud having a reduced end initially aligned in one of the openings.

' ROBERT G. FERRIS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 1,458,925 

